As the use of composite materials increases, the development of advanced nondestructive testing techniques for composite materials has also increased. Ultrasonic quantitative nondestructive testing techniques for composite materials can provide important information on manufacturing quality, material strength and useful lifetime. Porosity is one type of defect in composites that can be difficult to detect and measure. Porosity is typically caused by internal spaces (voids) within the composite material. Ultrasonic nondestructive testing techniques require a porosity reference standard to calibrate the measurements for a composite component provided by the ultrasonic testing equipment. It has been found, however, that the process of fabricating porosity reference standards can be complicated, time consuming and expensive. This process typically requires large numbers of composite coupons to be fabricated and many testing sites or samples to be taken for porosity measurements, and still will only result in a finite number of coupons. Selection of testing sites is essentially random, which requires iterations of coupon fabrication and porosity measurements to form reference standards representing a range of percent porosities.
Accordingly, there is a need for an improved way to generate porosity reference standards for use in ultrasonic nondestructive testing of composite materials.